The invention relates to an identification card having an embedded IC module for the processing of electrical signals.
The German Auslegeschrift No. 29 20 012 discloses an identification card having an embedded IC module. In this identification card, the module is attached to a separate carrier element along with all its leads and contacts, and is set into a window of the identification card, whereby the contact surfaces of the carrier element are located on the surface of the card and are freely accessible. IC modules of great complexity which are incorporated into identification cards should meet such requirements as needing little space, i.e. small dimensions for the component, and little energy consumption.
Complex integrated circuits having high packing density and little energy consumption are predominantly produced today with MOS technology.
As is generally known, MOS modules, i.e. circuits with high input resistance, are extremely sensitive to external electric fields or electrostatic charges.
There are therefore relevant regulations for dealing with IC modules with MOS technology, which must be strictly observed to protect the components. These concern both the production and storage and the processing of the IC module. Obviously, these regulations can only be partly observed when this type of module is incorporated into identification cards. In the above-mentioned publication, no particular protective steps are taken against possible damage of the IC module and contacts by external electric fields or electrostatic charges. Such fields and charges can endanger the sensitive module under unfavorable conditions even in normal daily use.
The potential danger for modules in MOS technology derives from the fact that the gate voltages may be between 20 and 500 V, depending on the type, and, due to the high input resistance, static charges are enough to make the voltage difference between the gate and the drain so large that the SiO.sub.2 depletion layer is punctured and the component is destroyed or damaged. Static charges of this order of magnitude are not unusual in daily use under certain environmental conditions. Especially in the case of plastic identification cards, the static charges produced by friction and so on are a potential source of danger for the operability of IC modules in identification cards.
The object of the invention is thus to protect the IC module in identification cards to a large extent against external electric fields and electrostatic charges.